Drop-on-demand thermal ink jet printers are generally well known, and in such systems, a thermal ink jet printhead comprises one or more ink filled chambers communicating with an ink supply chamber and an array of channels having open ends. A plurality of thermal transducers or heaters, usually resistors, are located beneath the channels at a predetermined location relative to the channels. The resistors are individually addressed with a current pulse thereby raising the temperature of the resistor and vaporizing the ink in contact with the resistor. A bubble is formed due to the heating of the ink. As the bubble grows, the ink bulges from the open end of the channel but is momentarily contained by the surface tension of the ink as a meniscus. As the bubble begins to collapse due to a drop in temperature of the resistor, the ink between the channel opening and the bubble starts to move towards the collapsing bubble, causing a volumetric contraction of the ink in the channel and resulting in the separation of the bulging ink as a droplet. The acceleration of the droplet out of the open end of the channel while the bubble is growing provides the momentum and velocity required for the droplet to travel in a substantially straight line direction towards a recording medium, such as paper.
A typical thermal ink jet printhead for use in an ink jet printer comprises an ink flow directing component, such as an etched silicon substrate which contains a linear array of channels open at one end and a common reservoir in communication with the channels, and a logic and thermal transducer component, such as a substrate which contains a linear array of heating elements, usually resistors, and monolithically integrated logic drivers and control circuitry. The components are aligned and mated with one resistor at each channel being located at a predetermined distance from the channel open end; the channel open ends serving as the droplet expelling channels or nozzles. Power MOS drivers immediately next to and integrated on the same substrate as the array of resistors are driven by the control circuitry, also integrated on the same substrate, that selectively enable the drivers which apply current pulses to the resistors.
One known method of fabricating thermal ink jet printheads is to form a plurality of the ink flow directing components and a plurality of logic, driver, and thermal transducer components on respective silicon wafers, and then aligning and bonding the wafers together, followed by a process for separating the wafers into a plurality of individual printheads, such as by dicing. The individual printheads are used in one common design of printer in which the printhead is moved periodically across a sheet of paper to form the printed image, much like a typewriter. Individual printheads can also be butted together side by side, placed on a supporting substrate, aligned, and permanently fixed in position to form a large array thermal ink jet printhead or a page width array printhead.
In U.S. Pat. No. 4,463,359 to Ayata et al., a drop on demand type ink jet recording method and apparatus which causes droplet emission from a small orifices is described. A drive signal is applied to the ink in a small liquid chamber to cause bubble formation in the ink which expels the ink from the orifice.
U.S. Pat. No. 4,638,337 to Torpey et al. describes an improved thermal ink jet printhead which prevents the sudden release of vaporized ink to the atmosphere, known as blowout, which causes ingestion of air and interrupts printhead operation.
U.S. Pat. No. 4,678,529 to Drake et al. describes a method of bonding thermal ink jet printhead components together by applying an adhesive to only higher surfaces of a substrate containing ink bearing structures, while all the surfaces of the ink bearing structures are free of adhesive.
U.S. Pat. No. Re. 32,572 to Hawkins et al. describes an ink jet printhead for high resolution printing made by concurrent fabrication of large quantities of printheads from two substrates that are preferably silicon wafers. A plurality of sets of bubble generating heating elements and their addressing electrodes are formed on one substrate and a corresponding plurality of sets of ink channels and their ink supplying manifolds are formed on another substrate.
U.S. Pat. No. 4,774,530 to Hawkins describes an ink jet printhead having electrode passivation and an elongated recess to provide an ink flow path between an ink manifold and individual ink channels by the placement of a thick film organic structure.
U.S. Pat. No. 4,829,324 to Drake et al. describes a large array thermal ink jet printhead and a fabrication process to provide precision assembly of the printhead using a subunit approach.
U.S. Pat. No. 5,000,811 to Campanelli et al. describes a fabrication approach for large array or page width thermal ink jet printheads in which wafer subunits are diced precisely for alignment and subsequent fabrication.
U.S. Pat. No. 5,010,355 to Hawkins et al. describes a two part thermal ink jet printhead in which one part contains ink flow directing channels, nozzles, and ink supplying reservoir, and the other part contains heating elements and ionic passivation of electronic driving circuitry.
U.S. Pat. No. 5,160,403 to Fisher et al. describes methods of fabricating ink jet printheads which can be butted against an aligning substrate to form an extended staggered array printhead.